This rule is triggered when the symbols used in the document for strong do not
match the configured strong style:

```markdown
**Text**
__Text__
```

To fix this issue, use the configured strong style throughout the document:

```markdown
**Text**
**Text**
```

The configured strong style can be a specific symbol to use ("asterisk",
"underscore"), or can require that usage be consistent within the document.

Rationale: Consistent formatting makes it easier to understand a document.